A respirator with an inhalation line, an exhalation line, a metering means for inhaled gas, as well as an exhalation valve that can be actuated has been known from DE 195 16 536 C2, with which both a volume-controlled and pressure-controlled respiration can be performed. Both the breathing gas flow and the breathing gas pressure are monitored during the respiration. A stenosis and disconnection alarm device as well as a pressure relief valve are usually present as safety and monitoring means. The pressure relief valve is used to reduce excess pressure during the inhalation phase and to limit them to a predetermined limit value. A pressure-limiting valve of this type is shown as an example in DE 28 01 546 C2.
An excessively high respiration pressure may have various causes. For example, the breathing gas flow is set to an excessively high value or the inhalation tube leading to the patient is kinked. However, cases of application in which a rapid pressure relief of the breathing gas-carrying components must be performed are also conceivable, e.g., in the case of the sudden onset of spontaneous respiratory activity or cough-related gasps. An overpressure limitation alone is not sufficient in these cases. On the other hand, it must also be ensured that the patient can exhale at any time. Exhalation via the exhalation valve is no longer possible in the case of a partially or completely kinked exhalation tube, and the pressure relief valve remains closed until the maximum pressure set is reached.